Pinpointing a powerline fault — in minutes
Scientists from Monash University have developed technology that can pinpoint the location of a powerline fault in minutes — a significant breakthrough given that repair crews can spend hours patrolling tens of kilometres of powerlines, some inaccessible by road, to find the source of the problem.
Given that some of Victoria’s worst bushfires have been started by powerlines, power distribution companies have installed devices that will limit the energy flowing to a fault to cut the fire risk. While this increases community safety, it also means communities might experience lengthy power outages while network operators attempt to track down the fault.
“In trials in China and Switzerland we demonstrated that our technology can find the fault location to within hundreds of metres in a few minutes, instead of hours or days,” said Monash University engineering researcher Dr Reza Razzaghi.
“In Australia, that would allow power to be restored to the community quickly, which can be vitally important for air conditioning during extreme heat, for people who rely on life-supporting electric medical devices, and for the many other home and business users.”
Since Australian grids have different characteristics from those in the trial countries, a proof-of-concept project was undertaken recently, supported by the Centre for New Energy Technologies (C4NET) and two major distribution network service providers in Victoria.
Razzaghi’s theoretical work on the technology is also being supported by an Australian Research Council (ARC) Discovery Early Career Researcher Award (DECRA). The theoretical advances made through the project will form a crucial step in developing commercial products to pinpoint powerline faults at scale in real electricity networks, specifically for an Australian context.
Inside the technology
Following the Black Saturday fires, Victoria’s distribution network service providers widely adopted devices called rapid earth fault current limiters (REFCLs) across power networks in high-fire-risk areas. These devices are installed at substations and function like a safety switch. When a fault is detected on one of the three wires that make up a high-voltage power distribution line, the device rapidly reduces the amount of energy flowing to the fault.
Since their rollout, REFCLs have been effective in reducing fire risks associated with powerline faults. However, in networks with REFCLs, faults leave little or no visible evidence, which leads to repair crews undertaking potentially long and arduous searches in order to find the problem.
A fault in a powerline, caused say by a falling tree, generates a series of characteristic electrical signals that travel on the line. Razzaghi and his team realised that they could analyse these signals to locate the fault.
They used a technique known as time reversal, which has been employed in other applications such as medical imaging and telecommunications.
“Our system automatically records and analyses the fault signals propagating through the powerline,” Razzaghi said. “Then it uses a model of the power network in an embedded computer to play back the signal transmission in reverse. This involves many real-time calculations, but in seconds to minutes it can locate the fault, to within hundreds of metres.”
While competing technologies are in development, the advantage of the time reversal technology is that it requires far fewer devices to be installed in a power network. This was demonstrated during the team’s extensive trial in Switzerland, where tests involved a mixed overhead and underground 22 kV distribution network. Installed in a zone substation, the fault location technology successfully found the location of faults in the branched network.
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